Fume exhaust system for cooking fumes

ABSTRACT

A fume exhaust system includes a fume filter, particularly, an odor filter that induces a catalysis process with the aid of catalyst material of the filter given irradiation of the fume exhaust stream with UV light and/or given ionization of the fume exhaust stream.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of copending International Application No. PCT/EP00/10032, filed Oct. 11, 2000, which designated the United States.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0002] The invention relates to a fume exhaust system for cooking fumes, containing a filtering device with at least one filter in the exhaust path with a catalyst material.

[0003] German Published, Non-Prosecuted Patent Application DE 23 63 820 discloses a fume exhaust hood with an odor filtering unit, that includes a sheet frame terminated on both sides by a fine wire mesh and filled with an odor filtering material. The odor filtering unit is disposed downstream from a grease filter in the fume exhaust path. The fume filter material is of such a type that it can be heated by a heating device enough to release its odorous substances and then be capable of picking up odorous substances again.

[0004] German Patent DE 31 46 537 C describes an odor filter that has active carbon as the filter material. Active carbon is non-regenerable and must, therefore, be replaced from time to time.

[0005] There are fume exhaust systems in the form of circulating air hoods and exhaust air hoods as well as in the form of hoods that can be optionally switched to recirculate or exhaust. They are disposed over ranges, stoves, and other devices for cooking food for the purpose of drawing off vapors, greases, and odors that arise in the cooking process. The exhaust air hoods send the drawn-in vapor out of the appertaining building and into the outside environment through an exhaust channel (exhaust chimney flue). Circulating air hoods conduct a portion of air that is contained in the vapor back into the room (kitchen) from which it was drawn after it is scrubbed by a filtering device.

[0006] Prior art circulating air hoods are far less effective than exhaust air hoods with respect to eliminating vapors, grease, and odors from the room where the hood is disposed over a range, stove, or other device for cooking food, i.e., the kitchen. But at the same time, there exists a high demand for an effective elimination of vapors, grease, and odor even by circulating air hoods, particularly in rental apartments, where it is not possible to cut through walls, or in low-energy houses, where energy loss should be prevented by avoiding the blowing of warm kitchen air into the outside atmosphere.

[0007] Circulating air hoods currently work primarily with active carbon filters for odor elimination. Disadvantages of such devices are described in the following text.

[0008] 1. The odor filter must be replaced every three to six months, the active surface having become saturated with gases (also referred to as “odors”) and grease. Such replacement is expensive and pollutes the environment. The deodorizing effect is imperfect and quickly deteriorates, so that the useful lives (effective usage periods) are rather short.

[0009] 2. Due to the high air resistance of active carbon filters, which are mostly bulk carbon filters with two densely pored fleece layers, the suction effect of circulating air filters is considerably smaller than that of exhaust air filters and diminishes sharply as the filter becomes dirtier. The noise generated by the fume exhaust hood, in particular, the flow noises of the fume exhaust stream and the motor noise of the fan in the fume exhaust hood, also increases sharply with increasing air resistance.

SUMMARY OF THE INVENTION

[0010] It is accordingly an object of the invention to provide fume exhaust system for cooking fumes that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that offers an alternative by which the utilization of disposable filters is avoided, odor elimination is improved, the overall effectiveness of the fume exhaust is improved, and the noise generation is reduced.

[0011] With the foregoing and other objects in view, there is provided, in accordance with the invention, a filtering system for a fume exhaust stream of a fume exhaust system, including at least one filter having a catalyst material, and an ionization source ionizing the fume exhaust stream, the ionization source disposed at the filter to induce a catalytic decomposition of at least one component of the fume exhaust stream with the catalyst material.

[0012] With the objects of the invention in view, there is also provided a filtering system for a fume exhaust stream of a fume exhaust system, including at least one filter having a catalyst material and an adsorption material adsorbing components from the fume exhaust stream, the adsorption material being desorbable to remove adsorbed components from the adsorption material, at least one of a UV light source irradiating the fume exhaust stream with UW light and an ionization source ionizing the fume exhaust stream to induce catalytic decomposition of at least one component of the fume exhaust stream with the catalyst material, and the UV light source or the ionization source being disposed at the filter.

[0013] The invention herein described is advantageous particularly for circulating air hoods but can also be utilized for exhaust air hoods in order to avoid polluting the environment outside a building.

[0014] The fume exhaust system can take the form of a hood as in the prior art or another form. As such, it will be referred to hereinafter as a fume exhaust system.

[0015] In accordance with another feature of the invention, the ionization source and/or the UV light source is/are disposed upstream of the filter with respect to a fume exhaust stream flow direction.

[0016] In accordance with a further feature of the invention, the filter is an odor filter and the catalyst material is of a material catalytically decomposing an odor component of the fume exhaust stream.

[0017] In accordance with an added feature of the invention, the filter has a lattice structure defining openings and the fume exhaust stream passes through the openings.

[0018] In accordance with an additional feature of the invention, the lattice structure is a honeycomb structure.

[0019] In accordance with yet another feature of the invention, the filter has a carrier lattice onto which the catalyst material is applied.

[0020] In accordance with yet a further feature of the invention, the carrier lattice is of one of the group consisting of metal and ceramic.

[0021] In accordance with yet an added feature of the invention, there is provided a material doped with the catalyst material, the material being applied to the carrier lattice.

[0022] In accordance with yet an additional feature of the invention, the material is ceramic.

[0023] In accordance with again another feature of the invention, the ceramic is zeolite ceramic.

[0024] In accordance with again a further feature of the invention, the catalyst material is titanium dioxide.

[0025] In accordance with again an added feature of the invention, the filter has an adsorption material for adsorbing components from the fume exhaust stream and the adsorbed components are desorbable by heating the filter to a temperature in a range between 120° C. and 180° C.

[0026] With the objects of the invention in view, there is also provided a fume exhaust system for cleaning a fume exhaust stream including a filtering system for filtering the fume exhaust stream, the filtering system having at least one filter having a catalyst material and an ionization source ionizing the fume exhaust stream, the ionization source disposed at the filter to induce a catalytic decomposition of at least one component of the fume exhaust stream with the catalyst material, and a fan fluidically connected to the filtering system for drawing the fume exhaust stream through the filtering system.

[0027] With the objects of the invention in view, there is also provided a fume exhaust system for cleaning a fume exhaust stream including a filtering system for filtering the fume exhaust stream, the filtering system having at least one filter having a catalyst material and an adsorption material adsorbing components from the fume exhaust stream, the adsorption material being desorbable to remove adsorbed components from the adsorption material, at least one of a UV light source irradiating the fume exhaust stream with UV light and an ionization source ionizing the fume exhaust stream to induce catalytic decomposition of at least one component of the fume exhaust stream with the catalyst material, and the at least one of the UV light source and the ionization source being disposed at the filter, and a fan fluidically connected to the filtering system for drawing the fume exhaust stream through the filtering system.

[0028] Other features that are considered as characteristic for the invention are set forth in the appended claims.

[0029] Although the invention is illustrated and described herein as embodied in fume exhaust system for cooking fumes, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

[0030] The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The figure is a diagrammatic, cross-sectional view of the fume exhaust system according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Referring now to the single figure of the drawing, it is seen that a fume exhaust system has a fume exhaust path, i.e., its air exhaust path, the fume exhaust system or hood 2 represented has, in succession in the direction of flow, a grease filter 4 and a regenerable odor filter 6, which are easy to remove and insert, a fan 12 that draws cooking fumes 8 and environmental air 10, an air vent 14 for letting scrubbed air 16 back into the space in which the fume exhaust hood 2 is located, and/or an alternative air vent 18 for letting scrubbed air 20 (or unscrubbed air 20 if the fume exhaust system 2 is being used without the filters 4 and 6) out of the space where the fume exhaust system 2 is located and into the outside atmosphere of the building.

[0033] The odor filter 6 includes catalyst material or is of catalyst material that exerts a catalyzing effect on the fume exhaust stream, which is composed of cooking fumes 8 and/or environmental air 10, namely on the odors (i.e., the odiferous gases) contained therein. The catalyzing effect is induced by the irradiating of the fume exhaust stream 8, 10 with ultraviolet light 22 (UV light) from a UV light source 24 directly in front of or at the regenerable odor filter 6. The UV light source 24 can be disposed at or in a housing 26 of the fume exhaust system 2 and fixed there, or externally, for instance on a wall of the building.

[0034] According to another embodiment of the invention, instead of the UV light source 24 an ionizing device 24 is provided to ionize the fume exhaust stream 8, 10 on the way to the odor filter 6 or directly at the odor filter 6.

[0035] The odor filter 6 is a regenerative filter functionally based on adsorption and catalytic oxidation.

[0036] The odor filter 6 preferably has a lattice structure, for instance, a honeycomb structure. The structure is advantageously formed by a metal or ceramic carrier structure on which a layer of catalyst material or other material that is doped with catalyst material (preferably, zeolite ceramic or titanium dioxide) is applied.

[0037] Such a latticed odor filter 6 has only a small flow resistance for the cooking fumes 8 and the environmental air 10, and a good adsorption effect for trapping adsorbable components of the cooking fume air stream. But the catalytic effect is only slight or is limited to light molecular structures (CH_(x), CH₄OH) at room temperature if no additional measures are provided. However, heating the cooking fume/environmental air stream, for instance, to 300° C., to trigger a catalytic effect is uneconomical due to the energy needed to accomplish the heating, and unfavorable due to the high temperature.

[0038] The techniques of UV radiation and ionization are, therefore, inventively proposed and it is possible to apply these alternatively or simultaneously for the purpose of inducing the catalysis process.

[0039] To induce the catalysis process by irradiating the air stream that is to be scrubbed with UV light upstream or in the region of the regenerable odor filter 6, the UV light can be generated by a commercial UV tube disposed behind a glass with good UV-light permeability and, thus, outside the steam region or fume region of the cooking fume 8. Given a suitable selection of the wavelength of the UV light in dependence upon the catalyst material, the portion of catalyzed gas in the fume exhaust stream being scrubbed can also include heavy molecular structures such as those arising in cooking processes. The catalyst material, for instance, titanium dioxide, is preferably doped in another material, for instance, in zeolite-ceramic as described above, which is applied to a metal or ceramic honeycomb structure or other lattice structure. As such, the portion of the odor filter 6 that is needed for the active surface for adsorption purposes is smaller than in conventional active carbon filters, or given equally large active adsorption surfaces of the odor filter 6, longer useful lifetimes are achieved (longer times for which the odor filter can be effectively utilized). When the odor filter 6 is saturated with respect to its adsorption capacity, which will occur in an estimated 30 to 40 operating hours (similar to grease filters), a regeneration is possible.

[0040] For such regeneration, in a first step, the grease can be removed from the odor filter 6 in a dishwasher because the lattice material utilized, including the catalyst material, is dishwasher-safe. In a second step, the odor filter 6 can be desorbed in the baking oven 30 of a stove 32 at approximately 150° C., i.e., the material that was adsorbed from the scrubbed air stream can be removed from the odor filter again.

[0041] By inducing the catalytic action by the abovementioned ionization it is also possible to accelerate the oxidation process by ionizing the air stream being scrubbed upstream or in the region of the regenerable odor filter 6 that includes the catalyst material. On one hand, the energy level is raised, even of larger molecules or particles of the fume exhaust stream 8, 10 being scrubbed, whereby they become more reactive, while, on the other hand, native oxygen and, depending on the ionization voltage, ozone, form by dissociation. Oxidation in the presence of the catalyst material of the odor filter 6 is, thus, furthered. Due to the furthering of oxidation, O₃ and higher-grade oxygen clusters can already oxidize. The similarly provided adsorption effect of the odor filter 6 causes the adsorption of uncatalyzable odors, i.e., gases. These adsorbed odors or odor particles can be desorbed in a baking oven at 150° C., as described above with respect to the irradiation with UV light. Excess ozone is converted into O₂ at room temperature by the catalytic component.

[0042] The particular advantages of the invention include the elimination of disposable filters. As such, there is a cost advantage for customers and a reduction of environmental pollution. The regeneration of the odor filter 6 can be performed easily, for instance, by washing the odor filter in a dishwasher and performing desorption in a baking oven. The invention also results in a better, more effective elimination of odors from the air stream that is scrubbed. A final advantage lies in the decreased flow resistance of the odor filter 6 relative to an active carbon filter. Due to the decrease in resistance, the electricity required for the fan 12, the fan noise, and the noise of the fume exhaust stream 8, 10 are reduced. 

I claim:
 1. A filtering system for a fume exhaust stream of a fume exhaust system, comprising: at least one filter having a catalyst material; and an ionization source ionizing the fume exhaust stream, said ionization source disposed at said filter to induce a catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material.
 2. The filtering system according to claim 1, wherein said ionization source is disposed upstream of said filter with respect to a fume exhaust stream flow direction.
 3. The filtering system according to claim 1, wherein: said filter is an odor filter; and said catalyst material is of a material catalytically decomposing an odor component of the fume exhaust stream.
 4. The filtering system according to claim 1, wherein: said filter has a lattice structure defining openings; and the fume exhaust stream passes through said openings.
 5. The filtering system according to claim 4, wherein said lattice structure is a honeycomb structure.
 6. The filtering device according to claim 1, wherein said filter has a carrier lattice onto which said catalyst material is applied.
 7. The filtering system according to claim 6, wherein said carrier lattice is of one of the group consisting of metal and ceramic.
 8. The filtering system according to claim 6, including a material doped with said catalyst material, said material being applied to said carrier lattice.
 9. The filtering system according to claim 8, wherein said material is ceramic.
 10. The filtering system according to claim 9, wherein said ceramic is zeolite ceramic.
 11. The filtering system according to claim 1, wherein said catalyst material is titanium dioxide.
 12. The filtering system according to claim 1, wherein: said filter has an adsorption material for adsorbing components from the fume exhaust stream; and the adsorbed components are desorbable by heating said filter to a temperature in a range between 120° C. and 180° C.
 13. A filtering system for a fume exhaust stream of a fume exhaust system, comprising: at least one filter having: a catalyst material; and an adsorption material adsorbing components from the fume exhaust stream, said adsorption material being desorbable to remove adsorbed components from said adsorption material; at least one of: a UV light source irradiating the fume exhaust stream with UV light; and an ionization source ionizing the fume exhaust stream, to induce catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material; and said at least one of said UV light source and said ionization source being disposed at said filter.
 14. The filtering system according to claim 13, wherein said at least one of said UV light source and said ionization source is disposed upstream of said filter with respect to a fume exhaust stream flow direction.
 15. The filtering system according to claim 13, wherein: said filter is an odor filter; and said catalyst material is of a material catalytically decomposing an odor component of the fume exhaust stream.
 16. The filtering system according to claim 13, wherein: said filter has a lattice structure defining openings; and the fume exhaust stream passes through said openings.
 17. The filtering system according to claim 16, wherein said lattice structure is a honeycomb structure.
 18. The filtering device according to claim 13, wherein said filter has a carrier lattice onto which said catalyst material is applied.
 19. The filtering system according to claim 18, wherein said carrier lattice is of one of the group consisting of metal and ceramic.
 20. The filtering system according to claim 18, including a material doped with said catalyst material, said material being applied to said carrier lattice.
 21. The filtering system according to claim 20, wherein said material is ceramic.
 22. The filtering system according to claim 21, wherein said ceramic is zeolite ceramic.
 23. The filtering system according to claim 13, wherein said catalyst material is titanium dioxide.
 24. The filtering system according to claim 13, wherein: said filter has an adsorption material for adsorbing components from the fume exhaust stream; and the adsorbed components are desorbable by heating said filter to a temperature in a range between 120° C. and 180° C.
 25. A fume exhaust system for cleaning a fume exhaust stream, comprising: a filtering system for filtering the fume exhaust stream, said filtering system having: at least one filter having a catalyst material; and an ionization source ionizing the fume exhaust stream, said ionization source disposed at said filter to induce a catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material; and a fan fluidically connected to said filtering system for drawing the fume exhaust stream through said filtering system.
 26. A fume exhaust system for cleaning a fume exhaust stream, comprising: a filtering system for filtering the fume exhaust stream, said filtering system having: at least one filter having: a catalyst material; and an adsorption material adsorbing components from the fume exhaust stream, said adsorption material being desorbable to remove adsorbed components from said adsorption material; at least one of: a UV light source irradiating the fume exhaust stream with UV light; and an ionization source ionizing the fume exhaust stream, to induce catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material; and said at least one of said UV light source and said ionization source being disposed at said filter; and a fan fluidically connected to said filtering system for drawing the fume exhaust stream through said filtering system.
 27. In a fume exhaust hood, a fume exhaust system comprising: a filtering system for filtering the fume exhaust stream, said filtering system having: at least one filter having a catalyst material; and an ionization source ionizing the fume exhaust stream, said ionization source disposed at said filter to induce a catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material; and a fan fluidically connected to said filtering system for drawing the fume exhaust stream through said filtering system.
 28. In a fume exhaust hood, a fume exhaust system comprising: a filtering system for filtering the fume exhaust stream, said filtering system having: at least one filter having: a catalyst material; and an adsorption material adsorbing components from the fume exhaust stream, said adsorption material being desorbable to remove adsorbed components from said adsorption material; at least one of: a VW light source irradiating the fume exhaust stream with UV light; and an ionization source ionizing the fume exhaust stream, to induce catalytic decomposition of at least one component of the fume exhaust stream with said catalyst material; and said at least one of said UV light source and said ionization source being disposed at said filter; and a fan fluidically connected to said filtering system for drawing the fume exhaust stream through said filtering system. 